Impact tools or apparatus

ABSTRACT

The invention is for an impact tool comprising a pressure fluid operating piston and cylinder device in which pressure fluid, for the cyclic operation of said device, is controlled by control means responsive to changes in fluid pressure brought about by relative reciprocatory movement between the piston and cylinder. In one preferred embodiment of the invention said control means comprises a valve means for controlling the supply of pressure fluid to the cylinder, for the retraction of the piston, and for controlling the exhausting of said pressure fluid from the cylinder, for the advance of the piston, a chamber or chambers connected to the cylinder so that a fluid therein will be subjected to pressure changes by movement of the piston, and means responsive to pressures in said chamber or chambers and operative cyclicly to switch said valve means between a pressure fluid supply position and a pressure fluid exhaust position. Conveniently said chamber or chambers is or are connected to the cylinder so that the fluid in said chamber or chambers will be compressed by retraction of the piston. The pressure fluid, for the operation of the tool, may be a liquid and the fluid in the chamber or chambers, which is compressible, may be a gas. Alternatively the pressure fluid, for the operation of the tool, may be a compressible liquid and the fluid in the chamber or chambers a similar compressible liquid.

United StatesPatent 1 A Philli s A r. 2 1974 [54] IMPACT TOOLS OR APPARATUS [57] ABSTRACT [75] Inventor: Reginald Andrew Phillips,

Warrington, England The invention is for an impact tool comprising a pres- [73] Assigneez Dobson Park Industries Limited, sure fluid operating piston and cylinder device in Nottingham, England [22] Filed: Jan. 18, 1972 [21] Appl. No.: 218,671

[30] Foreign Application Priority Data Feb. 10, 1971 Great Britain 4326/71 [52] U.S. Cl 91/165, 91/305, 91/308, 91/317 [51] Int. Cl. F01! 25/00 [58] Field of Search 91/317, 299,306, 305, 91/308, 165, 166

.[56] References Cited UNITED STATES PATENTS 3,225,663 12/1965 Pelisson 91/305 3,540,348 11/1970 Pennther 91/317 3,620,l26 ll/l97l Fuhrimann 91/306 FOREIGN PATENTS OR APPLICATIONS 784,684 10/1957 Great Britain 91/317 937,206 9/1963 Great Britain 91/308 Primary Examiner-Paul E. Maslousky Attorney, Agent, or Firm-Berman, Davidson and Bennan which pressure fluid, for the cyclic operation of said device, is controlled by control means responsive to changes in fluid pressure brought about by relative reciprocatory movement between the piston and cylinder. In one preferred embodiment of the invention said control means comprises a valve means for controlling the supply of pressure fluid to the cylinder, for the retraction of the piston, and for controlling the exhausting of said pressure fluid from the cylinder, for the advance of the piston, a chamber or chambers connected to the cylinder so that a fluid therein will be subjected to pressure changes by movement of the piston, and means responsive to pressures in said chamber or chambers and operative cyclicly to switch said valve means between a pressure fluid supply position and a pressure fluid exhaust. position. Conveniently said chamber or chambers is or are connected to the cylinder so that the fluid in said chamber or chambers will be compressed by retraction of the piston. The pressure fluid, for the operation of the tool, may be a liquid and the fluid in the chamber or chambers, which is compressible, may be a gas. Altematively the pressure fluid, for the operation of the tool, may be a compressible liquid and the fluid in the chamber or chambers a similar compressible liquid.

12 Claims, 6 Drawing Figures PATENTED APR 2 i974 SHEET 1- BF 5 PATENTEDAPR 2 I974 SHEU 2 [1F 5 1 IMPACT TOOLS OR APPARATUS This invention is for improvements in or relating to impact tools or apparatus hereinafter referred to as an impact tool. One particular application of the invention is to a tool for driving a chisel or the like into hard or rocky material for the breaking down thereof.

According to the present invention there is provided an impact tool comprising a pressure fluid operated piston and cylinder device, wherein pressure fluid for the cyclic operation of said device is controlled by means responsive to changes in fluid pressure brought about by relative reciprocatory movement between the piston and cylinder.

According to a further feature of the invention there is provided an impact tool comprising a cylinder, a piston which works in said cylinder, valve means for controlling the supply of pressure fluid to the cylinder, for the retraction of the piston, and for controlling the exhausting of said pressure fluid from the cylinder, for the advance of the piston, a chamber or chambers connected to said cylinder so that a fluid therein will be subjected to pressure changes by movement of the piston, and means responsive to pressures in said chamber or chambers and operative cyclicly to switch said valve means between a pressure fluid supply position and apressure fluid exhaust position. Conveniently said chamber or chambers is or are connected to the cylinder so that the fluid therein will be compressed by retraction of the piston. I

According to a still further feature of the invention there is provided an impact tool comprising a cylinder, a piston which works in said cylinder, valve means for controlling the supply of pressure fluid to the cylinder, for the retraction of the piston, and for controlling the exhausting of said pressure fluid from the cylinder, for

' the advance of the piston, a chamber or chambers for a compressible fluid connected to said cylinder so that a compressible fluid therein will be compressed by retraction of the piston, and means responsive to pressures in said chamber or chambers and operative cyclicly to switch said valve means between a pressure fluid supply position and a pressure fluid exhaust position. Y

Accordingto a still furtherfeature of the invention there is provided an impact tool comprising a cylinder, a piston which works in said cylinder, valve means for controlling the supply of pressure fluid to the cylinder for retraction of the piston, and for controlling the exhausting of said pressure fluid from the cylinder, for the advance of the piston, a chamber for a compressible fluid connected to said cylinder so that a compressible fluid within it will be compressed by retraction of the piston and means responsive respectively to high pressure in said chamber and a pressure change created in a part of the cylinder and operative cyclicly to switch said valve'means between a pressure fluid supply position and a pressure fluid exhaust position.

The invention will be further described, by way of example, with reference to the accompanying drawings in which:

F IG. 1 is alongitudinal sectional view of one form of impact tool according to the invention with its associated valves and pressure fluid circuitry shown diagrammatically,

FIG. 2 shows in section and in greater detail the valves associated with the tool shown in FIG. 1,

FIG. 3 shows in longitudinal section some modifications of and additions to the tool shown in FIG. 1,

I FIG. 4 shows a further modification of the tool shown in FIG. 1,

F IG. 5 shows diagrammatically one form of starting/- stopping arrangement for the tool, and

FIG. 6 shows an alternative starting/stopping arrangement for the tool.

The impact tool shown in FIG. 1 comprises a housing 10 having a first cylinder portion 10' in which works a piston 11 having a forward extension 12 of less diameter than the piston 11. At its rear end the housing 10 is provided, behind cylinder portion 10 and the piston 11, with a second cylinder portion 10 including a gas chamber 13.

At the forward end of the first cylinder portion 10 there is a holder 14 for a chisel or like tool 15. The chisel has a head 16 adapted to be struck, during operation of the tool, by the forward extension 12 of the piston 1 l.

Drains are provided at 17 and 18, in the first cylinder portion 10.

A port l9'is provided in the first cylinder portion 10 which communicates with the enlarged part 10a of said first cylinder portion. A passage 20 in the first cylinder portion wall connects the part 10a thereof to the part 10b of smaller diameter.

The flow of hydraulic pressure fluid, to and from the first cylinder portion 10' via the port 19, is controlled by a main control valve 21 which includes (see FIG. 2) a spool 22 which is operated by hydraulically driven pilot pistons 23 and 24. The main control valve 21 has a port 25 which is connected to a hydraulic main supply 26 and a port 27 which is connected to a hydraulic return main 28. Operation of the pistons 23 and 24, and thereby movement of the spool 22, 'is controlled by a high pressure pilot valve 29 and a low pressure pilot valve 30. The pilot valves 29 and 30 are connected by pipes 31 to the gas chamber 13 and respond, differentially, to high and low gas pressures therein so that said valves act, in effect, as high and low pressure gas operated switches. A hydraulic pilot start line 32 is connected to a port 33 of the low pressure pilot valve 30. This valve also has a port 34 connected to the cylinder of the pilot piston 24, in the main control valve, and a port 35 connected to a drain pipe 36.

The high pressure pilot valve 29 has a port 37 connected to the main supply pipe 26 and a port 38 connected to the return line 28. The high pressure pilot valve 29 also has a port 39 connected, through a spring loaded shuttle valve device 40, to the cylinder of the pilot piston 23 in the main control valve 21. The valve device 40 has a connection to a pilot piston reset line 41. The gas chamber 13 is provided with a gas inflation or charging device 400.

The operation of the tool above described is as follows:

As shown in the drawing the piston 11 is in the forward position and there is no pressure fluid supply to the tool. Immediately the pressure fluid supply is started the pilot pistons 23 and 24 take up the position shown in FIG. 2, if they are not already in that position, due to hydraulic pressure supplied over the pilot reset line 41.

Pressure fluid from the pilot start line 32 then acts, through the valve 30 which is in the position shown in FIG. 2, on the pilot piston 24 and moves the spool 22 to the left to admit pressure fluid to the first cylinder portion The piston 11, 12 is thus retracted causing the gas pressure in the chamber 13 to rise.

The rising gas pressure in the chamber 13 first cancels the pressure pilot signal, by raising the pilot valve 30, and then actuates the pilot valve 29 and pressure fluid then passes through the ports 37 and 39 to restore the spool valve 22, of the main control valve 21, to the position shown in FIG. 2. The piston 11, 12 then commences to make an impact stroke under the influence of the gas pressure in the chamber 13, and strikes the head 16 of the chisel 15.

As the gas pressure in the chamber 13 falls the pilot valves 29 and 30 return to the position shown in FIG. 2 and the next cycle starts automatically.

This automatic rapid high frequency cycling continues so long as the pressure fluid supply over the main supply line 26 and over pilot start line 32 is maintained.

The gas pressure settings of the pressure sensitive rams 29a and 30a of the pilot valves 29, 30 are adjustable by means of adjustably loaded springs associated with said rams. Actual pressure values are chosen to give best impacting. In this connection it may be of advantage to utilise pressure sensitive pilot valves of switching devices 29 and 30 which have an inherent lag characteristic which in other circumstances might be considered a defect.

It will be noted that the spool 22 of the main valve is designed to remain stationary in either position until one or other of the pilot pistons 23 or 24 is pressurised.

The modified embodiment of the invention shown in FIG. 3 is similar in many respects to the embodiment already described with reference to FIGS. 1 and 2 and when applicable like reference numerals have been used to designate like parts.

Referring to FIG. 3, a non return air inlet valve device is provided at 4112 to permit an inflow of air to the portion 100 of the first cylinder portion 10' and allow the piston to function as an air pump which tends to keep the front chamber at a higher pressure than the surrounding atmosphere, consequently inhibiting ingress of dirty air from the vicinity of impacting. Clean air can be ducted from a remote region.

Normally the chisel 16 is forced to the left, against or towards the back stop 45, for impacting, by pressing the tool against the rock or other face to be broken down. To provide for free air firing, however, a chiselbuffer is provided at 44 and the portion 10b of the first cylinder portion 10' is provided with a snubber reliefvalve 42 having a relief-valve damper bleed 43 for removing energy from the piston 11, 12.

The operative arrangement for the tool described above with reference to FIGS 1, 2 and 3 may be referred to as low pressure gas switching. An alternative arrangement which may be referred to as pulse switching will now be described. In this arrangement (see FIGS. 3 and 4) a chamber 10d, of somewhat smaller diameter than the main annulus 10a, is provided in the first cylinder portion l0.The requirement is to switch the main valve spool 22 at the end of the forward stroke of the piston 11. This is done by the creation of a pressure difference in chamber 10d. This pressure difference may act directly on the spool valve via a pipe 46, as shown in FIG. 4, or through a pilot valve 30 connected by a pipe 46a (see FIG. 3) to the portion 10d of the first cylinder portion.

To put the tool into operation the main valve spool 22 is pushed to the left (i.e. the position shown in FIG. 4) by an auxiliary piston or spring arrangement (not shown) to start the cycle in the normal way as above described. The spool 22 is hydrostatically balanced by means of port 48 and 49 connected into the main annulus 10a of the first cylinder portion.

At the end of the retraction stroke of the piston, high pressure gas switching of the spool 22, to the right, takes place as above described with reference to FIGS. 1, 2 and 3 and the piston 11 starts on its forward (impact) stroke, exhausting fluid through the port 49. Part way along the working stroke of the piston, the flow through port 49 is severely restricted by the piston entering the reduced bore diameter or snubbing chamber 10d. Exhaust fluid is then directed via conduit 46 into the end 24a of the spool valve casing or via pipe 46a to the pilot'valve 30, as the case may be, and the spool 22 is switched to the left. Surplus fluid passes via duct 50. An adjustable restrictor 51 in the duct 50 provides control of pressure rise in the connection 46. I

Duct 46 and port 48 are made large to minimise energy losses and it is believed that the exhaust pressure to operate the valve will be approximately the same as when exhausting normally.

A starting/stopping arrangement for the tool may comprise a full-flow stop valve 52, in the supply line 26, as shown in FIG. 5 or alternatively a stop valve 53 in the hydraulic pilot start line 32 as indicated in FIG. 6.

As an alternative to a gas the chamber 13 may be charged with a compressible liquid. In such a case and where the tool is adapted for hydraulic operation, it is advantageous if said liquid and the liquid for the operation of the tool are similar.

I claim:

1. An impact tool comprising a housing including a first cylinder portion and a second cylinder portion, a piston working in said first cylinder portion, the first cylinder portion having pressure fluid supply and exhaust means for the retraction and advancement of the piston respectively, a control valve means for said pressure fluid supply and exhaust means, pressure sensitive means operative to actuate said control valve means, means for supporting a tool to be struck by the piston when it is advanced, said second cylinder portion including a chamber positioned to receive the piston when it is retracted, a separate body of fluid permanently disposed in said chamber and compressed therein by retraction of the piston into said chamber, and connecting means between said chamber and said pressure sensitive means whereby said compression of said fluid in the chamber acts on said pressure sensitive means to actuate the control valve means to exhaust the first cylinder portion and allow the piston to advance under the action of said compressed fluid and make a stroke in the impacting direction, and the resultant fall of fluid pressure in the chamber causes said pressure sensitive means to allow the control valve means to actuate to supply pressure fluid. to the first cylinder portion for retraction of the piston thereby to cause cyclic operation of the tool.

2. An impact tool as claimed in claim 1 wherein the pressure fluid supply is a liquid and the fluid compressed in the chamber is a gas.

3. An impact tool as claimed in claim 1 wherein the pressure fluid supply is a liquid and the fluid compressed in the chamber is a similar liquid.

4. An impact tool as claimed in claim 1 wherein the pressure sensitive means is a pressure actuated pilot valve and the control valve means is a spool valve, a supply of pressure fluid to said spool valve for its operation, being controlled by said pilot valve.

5. An impact tool as claimed in claim 1 wherein the pressure sensitive means comprises pressure actuated pilot valves and the control valve means is a spool valve, a supply of pressure fluid to said spool valve, for its operation, being controlled by said pilot valves.

6. An impact tool as claimed in claim 5 wherein one of said pilot valves which actuates the spool valve to the exhaust position is a high pressure piston operated pilot valve and the other of said pilot valves, which actuates the spool valve to the pressure fluid supply position, is a low pressure piston operated pilot valve.

7. A impact tool as claimed in claim 1 wherein the control valve means comprises a spool valve which is operated from the pressure fluid supply to the pressure fluid exhaust position under the control of a high pressure piston-operated pilot-valve connected for its operation to said chamber, and from the pressure fluid exhaust to the pressure fluid supply position by causing the exhaust fluid to act on said spool valve.

8. An impact tool as claimed in claim 1, wherein the control valve means comprises a spool valve which is operated from the pressure fluid supply to the pressure fluid exhaust position under the control of a high pressure piston-operated pilot-valve connected for its operation to said chamber, and from the pressure fluid exhaust to the pressure fluid supply position by causing the exhaust fluid to act on a pilot valve controlling a supply of pressure fluid to the spool valve.

9. An impact tool as claimed in claim 4 wherein said pilot valve has a lag characteristic. 7

10. An impact tool as claimed in claim 1' wherein means is provided for the charging of said chamber with a compressible fluid.

11. An impact tool as claimed in claim 1 and having a non return air inlet to permit an inflow of air to a part of the first cylinder portion so that the piston can act as an air pump to keep said part of the first cylinder portion at a higher pressure than the surrounding atmosphere. I

12. An impact tool as claimed in claim 1 wherein the chamber of said second cylinder portion is a coaxial rearward extension of the first cylinder portion. 

1. An impact tool comprising a housing including a first cylinder portion and a second cylinder portion, a piston working in said first cylinder portion, the first cylinder portion having pressure fluid supply and exhaust means for the retraction and advancement of the piston respectively, a control valve means for said pressure fluid supply and exhaust means, pressure sensitive means operative to actuate said control valve means, means for supporting a tool to be struck by the piston when it is advanced, said second cylinder portion including a chamber positioned to receive the piston when it is retracted, a separate body of fluid permanently disposed in said chamber and compressed therein by retraction of the piston into said chamber, and connecting means between said chamber and said pressure sensitive means whereby said compression of said fluid in the chamber acts on said pressure sensitive means to actuate the control valve means to exhaust the first cylinder portion and allow the piston to advance under the action of said compressed fluid and make a stroke in the impacting direction, and the resultant fall of fluid pressure in the chamber causes said pressure sensitive means to allow the control valve means to actuate to supply pressure fluid to the first cylinder portion for retraction of the piston thereby to cause cyclic operation of the tool.
 2. An impact tool as claimed in claim 1 wherein the pressure fluid supply is a liquid and the fluid compressed in the chamber is a gas.
 3. An impact tool as claimed in claim 1 wherein the pressure fluid supply is a liquid and the fluid compressed in the chamber is a similar liquid.
 4. An impact tool as claimed in claim 1 wherein the pressure sensitive means is a pressure actuated pilot valve and the control valve means is a spool valve, a supply of pressure fluid to said spool valve for its operation, being controlled by said pilot vaLve.
 5. An impact tool as claimed in claim 1 wherein the pressure sensitive means comprises pressure actuated pilot valves and the control valve means is a spool valve, a supply of pressure fluid to said spool valve, for its operation, being controlled by said pilot valves.
 6. An impact tool as claimed in claim 5 wherein one of said pilot valves which actuates the spool valve to the exhaust position is a high pressure piston operated pilot valve and the other of said pilot valves, which actuates the spool valve to the pressure fluid supply position, is a low pressure piston operated pilot valve.
 7. A impact tool as claimed in claim 1 wherein the control valve means comprises a spool valve which is operated from the pressure fluid supply to the pressure fluid exhaust position under the control of a high pressure piston-operated pilot-valve connected for its operation to said chamber, and from the pressure fluid exhaust to the pressure fluid supply position by causing the exhaust fluid to act on said spool valve.
 8. An impact tool as claimed in claim 1, wherein the control valve means comprises a spool valve which is operated from the pressure fluid supply to the pressure fluid exhaust position under the control of a high pressure piston-operated pilot-valve connected for its operation to said chamber, and from the pressure fluid exhaust to the pressure fluid supply position by causing the exhaust fluid to act on a pilot valve controlling a supply of pressure fluid to the spool valve.
 9. An impact tool as claimed in claim 4 wherein said pilot valve has a lag characteristic.
 10. An impact tool as claimed in claim 1 wherein means is provided for the charging of said chamber with a compressible fluid.
 11. An impact tool as claimed in claim 1 and having a non return air inlet to permit an inflow of air to a part of the first cylinder portion so that the piston can act as an air pump to keep said part of the first cylinder portion at a higher pressure than the surrounding atmosphere.
 12. An impact tool as claimed in claim 1 wherein the chamber of said second cylinder portion is a coaxial rearward extension of the first cylinder portion. 